1. Field of the Invention
The present invention relates to an optical fiber having a hollow portion which extends along its axis, and to a production method therefor.
2. Description of the Background Art
Japanese Patent No. 3072842 discloses a single-mode optical fiber which includes a hollow core, and a cladding formed around the core, having a photonic band gap structure, and which propagates light by Bragg reflection. In this prior art, however, no consideration was given to the protection of the hollow portion in the optical fiber, which may result in the deterioration of the optical characteristics, for example, the optical loss may increase.